Helicobacter pylori (H. pylori) infection can lead to chronic active gastritis, which is characterized by striking infiltration of the gastric epithelium and the underlying lamina propria by neutrophils, T and B lymphocytes, macrophages, and mast cells. H. pylori infection can lead to the development of gastric ulcers, which can be deadly if perforated, and has been associated with the development of cancers in the gastrointestinal tract and stomach. Currently the pathogenic effects of H. pylori infection are poorly understood. For example, it is not clear whether the chronic gastritis that develops in certain infected individuals is due to the immune response to H. pylori causing damage to the stomach, or whether H. pylori infection leads to the development of autoimmune gastritis. [unreadable] [unreadable] We are using mouse models to study of H. pylori infection, pathogenic mechanism(s) and mucosal-immune responses. For this study we selected wild type (wt) C57BL/6 and C57BL/6 IL-10 knockout mice to evaluate the role of endogenous IL-10 on the regulation of mucosal immune response to H. pylori infection. The IL-10 knockout (IL-10-/-) mice allowed us to examine the in vivo role of interleukin 10 responses as it relates to bacteria load per gram of stomach tissue and pathology. [unreadable] In this study, we monitored histological changes by pathology scoring. In collaboration with Dr. Richard DiPaolo, Saint Louis University Medical School (formerly, NIAID), we have developed a new technique that allows us to isolate the inflammatory cells from the stomach mucosa of mice. Using this technique, we identify, quantify, and determine the functions and specificities of cells infiltrating the stomach after infection. We observed an increase in the number of CD4+ and CD8+ T cell infiltrating the stomach tissue of wt infected mice, 7 and 6 fold, respectively. [unreadable] The functional assays allowed us to examine the CD4+ and CD8+ T cell responses in the stomach after H. pylori infection. For example, using this technique we confirmed a previously reported observation that T cells infiltrating the stomach produce IFN (a T-helper type 1 response), but in addition, we made a new observation that there are T cells producing IL-17, and T cells producing both IL-17 and IFN. The discovery of IL-17 producing T cells is a novel finding and suggests an additional T-helper type 17 response to H. pylori infection. This is an important finding because IL-17 production has been associated with recruitment of neutrophils, causing and sustaining tissue damage related to various autoimmune disorders. The latter observation may provide a link between H. pylori infection and autoimmune gastritis. [unreadable] [unreadable] We are currently characterizing the immune response in H. pylori infected IL10-/- mice, and comparing this to wild type mice. Thus far, we found that despite having several orders of magnitude fewer H. pylori per gram of stomach tissue, the IL-10-/- mice have more cytokine producing (IFNg/IL17/TNFa) CD4+ and CD8+ T cells (5- and 4-fold, respectively than wt infected mice) in the stomach and a more severe gastritis. We will characterize these responses in greater detail to determine whether the CD4+ and CD8+ T cells infiltrating the stomachs in IL10-/- mice can transfer disease in non-infected mice. If so, this may indicate that lack of IL10 is a double edged sword in the face of infection, causing greater immunity to the pathogen (lower colony counts) but higher susceptibility to autoimmunity.[unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] We are also studying adaptive immunity as it relates to H. pylori infection. The cellular and molecular mechanism that initiates H. pylori adaptive immunity and dictates the T-cell response is poorly understood. Dendritic cells are central to the initiation of adaptive immunity. We have initiated in vitro studies to compare immune responses to H. pylori infection involving a common adaptor molecule, myeloid differentiation protein (MyD88) and selected Toll-like receptors. Our goal is to assess the relative contribution of MyD88 and Toll-like receptors 2 and 4 in the host response to H. pylori infection as well as monitor T-cell responses. [unreadable] [unreadable] Purified CD8+ or CD4+ T-cells from C57BL/6 mice were cocultured in vitro with bone marrow derived dendritic cells (DC) from MyD88-/-, TLR2-/-, TLR4-/-, TLR2-/-/TLR4-/- (double knockout animals) or wt C57BL/6 mice stimulated with inactivated H. pylori. IL-17 and IFN-gamma (IFNg) production were monitored by flow cytometry. We observed the following in vitro results for CD8+ T cells. A large number CD8+ T cells (range 25 to 8%) cocultured with dendritic cells from wt and TLR 2 and 4 mice produced significant amounts of IL-17 and IFNg. Significantly less CD8+ T-cells in coculture dendritic cells from MyD88 -/- mice produced IL-17 or IFNg, 0.9 % to 7%, respectively. Less CD4+ T-cell in dendritic cell cocultures, as described for CD8+ T-cells, produced IL-17 (range 1.3 to 0.63%) but CD4+ T-cells produced significant amount of IFNg (range 56 to 48%). IL-17 and IFNg production by CD4+ T-cells in coculture with DC from MyD88 knockout was significantly lower. These results suggest that the T-helper type IL-17immune response to H. pylori infection is primarily a CD8+ T-cells response. In addition, the T-helper IL-17 immunity is MyD88-dependent and may be partially dependent on Toll-like Receptors 2 and 4.